OFFSET
1,1
COMMENTS
A sequence related to A054356. These primes look like "EEhEEhEEE" when viewed upside down by rotation of 180 degrees (3343 - "EhEE", 3433 - "EEhE", 33343 - "EhEEE", 333433 - "EEhEEE").
REFERENCES
Giorgio Balzarotti, Paolo P. Lava, Centotre curiosità matematiche, Hoepli, 2010, pp. 3-4.
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
G. L. Honaker, Jr. and Chris Caldwell, Prime Curios!: 47
G. L. Honaker, Jr. and Chris Caldwell, Prime Curios!: 3343
MAPLE
S:= {}:
for n from 3 to 16 do
for k from 1 to floor((n-1)/2) do
for r in combinat:-choose(n-1-k, k) do
L:=subsop(seq(t=(3, 4), t=r), [3$(n-k)]);
x:= add(L[i]*10^(n-i), i=1..n);
if isprime(x) then S:= S union {x} fi
od od od:
sort(convert(S, list)); # Robert Israel, Mar 15 2016
MATHEMATICA
Select[Flatten[Table[FromDigits/@Select[Tuples[{3, 4}, n], SequenceCount[ #, {3, 4, 3}, Overlaps->True]==Count[#, 4]&], {n, 3, 11}]], PrimeQ]//Sort (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Sep 17 2016 *)
PROG
(Magma) [p: p in [3..33333333343 by 10] | (p mod 100 eq 33 or p mod 100 eq 43) and IsPrime(p) and Position(IntegerToString(p), IntegerToString(3)) eq 1 and Set(Intseq(p)) subset [3, 4] and not IntegerToString(44) in IntegerToString(p)];
CROSSREFS
KEYWORD
nonn,base,dumb
AUTHOR
Arkadiusz Wesolowski, Mar 15 2016
STATUS
approved